A complete non-invasive characterization by XRF, XRD, near-FTIR and UV–Vis reflectance spectroscopy has been performed on some commercially available violet pigments as well as on pure violet Co-salts also known to be used as pigments. The obtained results showthat, after a preliminary elemental characterization, the studied pigments can be easily identified by near-FTIR and UV–Vis spectroscopies since they exhibit peculiar spectral bands in these regions. Among the analyzed samples emerged that the pigment 45350 - “Manganviolett” from Kremer consists of two α- andβ-NH4MnP2O7 polymorphs, being α-NH4MnP2O7 the most abundant one; furthermorewe found that the pigment R1215D -“Cobalt violet” by Winsor & Newton (no longer available since 2006) displays spectral features that match exactly those of 45820-“Kobaltviolett hell” from Kremer and both are composed by cobalt ammonium phosphate hydrate. Such non-invasive study allowed for the identification of “Manganese Violet” (α-NH4MnP2O7) and anhydrous cobalt phosphate (Co3(PO4)2) on some Boccioni's paintings during MOLAB in situ measurements at the Museo del Novecento (Milano).
Molecular and structural characterization of some violet phosphate pigments for their non-invasive identification in modern paintings
VIVANI, Riccardo;ROMANI, Aldo;MILIANI, Costanza
2017
Abstract
A complete non-invasive characterization by XRF, XRD, near-FTIR and UV–Vis reflectance spectroscopy has been performed on some commercially available violet pigments as well as on pure violet Co-salts also known to be used as pigments. The obtained results showthat, after a preliminary elemental characterization, the studied pigments can be easily identified by near-FTIR and UV–Vis spectroscopies since they exhibit peculiar spectral bands in these regions. Among the analyzed samples emerged that the pigment 45350 - “Manganviolett” from Kremer consists of two α- andβ-NH4MnP2O7 polymorphs, being α-NH4MnP2O7 the most abundant one; furthermorewe found that the pigment R1215D -“Cobalt violet” by Winsor & Newton (no longer available since 2006) displays spectral features that match exactly those of 45820-“Kobaltviolett hell” from Kremer and both are composed by cobalt ammonium phosphate hydrate. Such non-invasive study allowed for the identification of “Manganese Violet” (α-NH4MnP2O7) and anhydrous cobalt phosphate (Co3(PO4)2) on some Boccioni's paintings during MOLAB in situ measurements at the Museo del Novecento (Milano).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
